SB 608 


c" v B i MITED STATES DEPARTMENT OF AGRICULTURE 



Wash'r.gbr, D. C. _▲ July 21, 1923 


A STUDY OF DECAY IN DOUGLAS FIR IN THE PACIFIC NORTHWEST. 

By J. S; Boyce, Pathologist , Office of Investigations in Forest Pathology , Bureau 

of Plant Industry. 


CONTENTS. 


Page. 


Importance of decay in Douglas fir. 1 

Method of collecting data. 2 

Fungi causing decay. 3 

Position of the decays in the tree. 4 

Relative importance of the decays. 4 

Mechanical injuries. 5 


Page. 


Entrance of the decays. 7 

Indications of decay In living trees. 10 

Extent of incipient decay. 15 

Summary. ig 

Outlook.17 

Literature cited.19 


IMPORTANCE OF DECAY IN DOUGLAS FIR. 

Douglas fir is the most important timber tree in the Pacific North¬ 
west, covering, as it does, the greater part of the foothills and lower 
slopes of the Cascade Mountains and the Coast Range in practically 
pure stands of great density. The stand of this species in Oregon and 
Washington is estimated at 505 billion feet ( 6 , p. 23), 1 or nearly one- 
fourth of the remaining merchantable timber in the United States. 

The loss through decay in Douglas fir in this region is very high. 
While some overmature stands are relatively sound a loss of 20 per 
cent in such stands is not uncommon. In certain cases the cull figure 
may reach 50 per cent or more, so high that in timber on difficult 
ground it becomes impossible to log at a profit. It is only in young 
stands of second growth that Douglas fir is uniformly sound. Plate 
I shows defective trees left uncut after logging in an overmature 
stand. In this instance about 25,000 feet board measure per acre 
was left standing. Where clear cutting is practiced numerous logs 
and entire trees remain on the ground after logging, absolutely worth¬ 
less on account of decay. This is illustrated in Plate II. Practically 
all the large pieces were left because of rot. 

Recognizing the importance of this question, foresters and lumber¬ 
men in the Douglas fir region have repeatedly felt the need for exact 
information on decay in Douglas fir. This bulletin presents obser¬ 
vations by the writer and the results of a preliminary study. 1 2 

1 The serial numbers (italic) in parentho-ej refer to “ Literature cited ” at the end of this bulletin. 

2 This study was made in the summer of 1917 under the direction of Dr. E. P. Meinecke. To him the 
writer is indebted for supervision and assistance throughout the course of the field work. The project 
was a cooperative one avith the Forest Service of the United States Department of Agriculture, and 
acknowledgment is made to Forest Examiner F. B. Kellogg for his part in collecting the field data. A 
much more detailed study of decay in Douglas fir is now in progress, but will not be completed for several 
years. 


H 




42198—23-1 


1 

























2 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 

METHOD OF COLLECTING DATA. 

The trees selected for study were part of a defective, overmature 
stand of pure Douglas fir on the west slope of the Cascade Mountains 
at McCredie Hot Springs, above Oakridge, Lane County, Oreg. 
The area was at an elevation of about 2,000 feet above sea level, and 
the local topography was characterized by moderate slopes and almost 
level benches. The stand was quite typical of the bulk of the Douglas 
fir type on the west slope of the Cascade Mountains. 

Each tree was felled with a stump height of lb feet measured at a 
point halfway on the slope. The hole was then cut into 16-foot logs 
to an 8-inch top-diameter limit inside the bark. Complete measure¬ 
ments were then taken. Next, the logs were split open and any 
further data available recorded. In this way it was possible to study 
each tree very completely, particularly with reference to the character 
and distribution of decay. Volumes of the trees were worked up in 
both board and cubic feet. The board-foot volume included the 
merchantable portion of each tree from the stump height of 1^ feet 
to a diameter limit of 8 inches inside bark. The 16-foot logs were 
scaled with the Scribner Decimal C scale and the volume of decay 
determined in accordance with the standard scaling practice of the 
Forest Service (5). 

The cubic-foot volume included the contents of the entire stem 
from the ground level to the tip. In computing volumes the stump 
was considered as a cylinder, each 16-foot log as the frustum of a 
paraboloid, applying the Smalian formula (2, p. 161), the top (that 
is, the section from the 8-inch diameter inside bark to the tip) as a 
cone, and a broken section of the top which did not include the tip 
as the frustrum of a cone. The actual cubic-foot volume of decay 
was computed by the same formulas. 

A general idea of the size and age of the trees analyzed is given 
in Table 1. 

Table 1— Size and age of Douglas fir trees studied. 


Age class. 

Average 

age 

(years). 

Average 

diameter 

breast 

high 

(inches). 

Percentage of 
total volume. 

Number 
of trees, 
basis. 

Cubic 

feet. 

Board 

feet. 

41 to 60 years. 

59 

9.5 

0.04 

0 

1 

61 to 80 years. 

68 

12.1 

.91 

0.62 

8 

81 to 100 years. 

95 

14.0 

.53 

.42 

3 

101 to 120 years. 

103 

16.3 

.75 

.62 

3 

121 to 140 years. 

129 

■ 16.0 

.15 

.11 

1 

141 to 160 years. 





(i) 

161 to 180 years. 





o 

181 to 200 years. 

195 

18.7 

1.36 

1.11 

5 

201 to 220 years. 

214 

25.3 

15.49 

14.89 

29 

221 to 240 years. 

230 

27.5 

32.69 

33.91 

47 

241 to 260 years. 

246 

27.9 

10.81 

11.20 

15 

261 to 280 years. 

271 

28.1 

15.81 

15.74 

25 

281 to 300 years. 

284 

29.2 

1.52 

1.63 

2 

301 to 320 years. 

309 

29.7 

6.07 

5.97 

9 

321 to 340 years. 

333 

29.8 

10.38 

10.22 

16 

341 to 360 years. 

348 

28.9 

2. 48 

2.46 

4 

361 to 380 years. 

362 

39.6 

1.00 

1.10 

1 

Combined. 

238 

26.1 



169 







i One tree, too small to consider. 


































DECAY IN DOUGLAS EIR. 


3 


.FV&fe 

The trees studied were not clear cut from a given area, but average 
trees both sound and decayed were selected to obtain preliminary 
information on which an extensive study of decay in Douglas fir 
could be based. This will be brought out as the discussion proceeds. 

In all 170 trees were felled, bucked up, split open, and studied. 
One of these was only 2 inches in diameter breast high, so it was 
dropped from consideration, leaving 169 trees with a total volume of 
203,920 feet board measure and 33,703.12 cubic feet. 

FUNGI CAUSING DECAY. 

Four species of fungi are responsible for all but an infinitesimal 
portion of the decay in Douglas fir. They are the ring-scale fungus 
(Trametes pini (Thore) Fr.), the velvet-top fungus (Polyporus schwei- 
nitzii Fr.), the quinine fungus (Fomes lands (Jacq.) Murr.), and the 
rose-colored Fomes (Fomes roseus (Alb. and Schw.) Cke.). The 
decays caused by these four wood-destroying fungi in living trees are 
confined to the heartwood. 

The ring-scale fungus causes decay commonly known as conk-rot 
in this region (ring-scale or red-rot in the pine regions), in which the 
wood is riddled with small white pits or cavities, apparently separated 
by sound wood. This is shown in Plate III, Figure 1. In its incip¬ 
ient stages, before the appearance of the white pits, the decay appears 
as a pronounced reddish purple or olive-purple discoloration, often 
bounded by a narrow zone of pronounced red color. The sporo- 
phores, or conks, are very common in overmature Douglas fir stands. 
These fruiting bodies issue from the tree through knots and are 
perennial. They vary in size and in shape from bracketlike to hoof 
shaped. The upper side is a dull grayish or brownish black, rough, 
and with concentric furrows parallel to the light-brown margin. The 
under side is a grayish brown or rich brown color with large irregular 
pores. The substance or context of the sporophores is corky or 
punky. Plate IV shows the appearance of the sporophores on a 
living tree. 

The velvet-top fungus causes a red-brown friable rot in the final 
stage. The incipient decay is very difficult to detect. It first becomes 
noticeable as a faint yellowing or browning of the normal heartwood, 
which still seems to be firm and hard but in reality is seriously weak¬ 
ened. The sporophores, or conks, of this wood destroyer appear 
either on the infected tree or on the ground near by and are annual. 
They are rather large, with a light-brown upper surface, an olive or 
dirty green under surface, and have a cheesy consistency when young, 
but when old and dry are a dark rusty brown and corky. Sporo¬ 
phores on the ground have a short thick stalk. Plate V, Figures 1 
and 2, illustrate both sporophores and decay of this fungus. 

The quinine fungus has a large, conspicuous, whitish perennial 
sporophore, not at all common on living trees. The substance of the 
sporophore is white, soft, and cheesy when young and rather crumbly 
and chalky when old and dry, with an exceedingly bitter taste. 
Hence the name. On the older sporophores the upper surface is 
rough and chalky white and brownish in color. The pores are small 
and regular. Plate VI, Figure 1, shows a sporophore. The typical 
decay is a crumbly brown rot easily recognizable by its mycelium 
felts or sheets (i. e., closely woven masses of fungus hyphse). This 
characteristic is brought out inPlate VI, Figure 2. The incipient decay 
which appears as a faint brownish discoloration is not easy to recognize. 


4 


BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 


The sporophores of the rose-colored Fomes are easily recognized by 
the delicate rose color of the under surface. The pores are small. 
The upper surface is rough, hard, and black. This is illustrated in 
Plate III, Figure 2. The decay caused by this organism is a yellow- 
brown crumbly rot, with mycelium felts much less conspicuous than 
those of the quinine fungus. The incipient decay is indicated by a 
faint brownish color, the outer limit of which is sometimes marked 
by a zone of brownish green discoloration. 

POSITION OF THE DECAYS IN THE TREE. 

The decay caused by the ring-scale fungus and that caused by the 
quinine fungus are not confined to any one portion of the bole but 
commonly extend throughout the tree. 

On the other hand, the decay caused by the velvet-top fungus is a 
typical butt-rot. Of the 70 infections of this decay in 68 trees, each 
separate focus of the rot in a tree being considered an infection, 94.3 
per cent, or all but 4, were in the stump or butt log. The decay 
usually does not extend higher than the first 16-foot log. In 10 trees 
only did the decay go beyond the butt log, and the greatest upward 
extent in any one case was 37.4 feet above ground level. The average 
for all the butt infections was 10.41 feet above the ground. The 
measurements given include the incipient decay. 

The decay caused by the rose-colored Fomes is usually confined to 
the upper portion of the tree in connection with dead tops, and often 
the rot does not extend into the merchantable portion of the infected 
tree. In all, there were 46 infections of this rot, and all but 9 of 
these were in the upper bole. Of those in the upper bole, 18, or 
almost 50 per cent, were in the top beyond the 8-inch diameter limit 
and caused no loss in merchantable volume. 

For the sake of brevity in the remainder of this paper, the decays 
caused by these four fungi will be designated as follows: 

Velvet-top fungus. red-brown butt-rot. 

Ring-scale fungus. conk-rot. 

Quinine fungus. brown trunk-rot. 

Rose-colored Fomes. yellow-brown top-rot. 

When used in tables the designations will be simply butt-rot, conk- 
rot, trunk-rot, and top-rot. 

RELATIVE IMPORTANCE OF THE DECAYS. 

Conk-rot is responsible for by far the greatest amount of cull in 
Douglas fir. In fact, if the species was free from this defect it would 
take its place with the pines as a sound tree. This is brought out in 
Table 2. 

In considering Table 2 it must be remembered that it is not based 
on trees clear cut from a given area. Consequently the figures on 
the percentage of infected trees and volume of decay are not indica¬ 
tive of the actual loss through decay in stands of Douglas fir, but 
they do indicate the relation of the various decays. Under “ unknown 
rots” are placed a number of small infections of decays whose cause 
could not be determined and one infection caused by Gqnoderma 
oreqonense Murr., which resulted in a slight loss. 

Conk-rot stands out as the all-important cause of decay. The 
volume destroyed by this decay in comparison with the others is far 






DECAY IN DOUGLAS FIR. 


5 


greater than the ratio of infected trees would indicate. For example, 
only about one-third more trees are infected with conk-rot than with 
red-brown butt-rot, yet the board-foot volume of decay is slightly 
more than 18 times as great. Conk-rot is usually quite extensive in 
an infected tree, particularly in the mechantable portion of the bole. 


Table 2. —Relative importance of the different kinds of decay in Douglas fir. 



Volume of decay, 
percentage of gross 

Infected 
trees, 
percent¬ 
age of 
total. 


Infections. 


Kinds of decay. 

volume. 



Average volume. 



Number 

basis. 

Percent¬ 




Board 

feet. 

Cubic 

feet. 

age of 
total. 

Board 

feet. 

Cubic 

feet. 

Conk-rot. 

38.4 

22.5 

61.0 

118 

41.6 

663 

64.2 

Trunk-rot. 

2.7 

1.3 

! 5.9 

15 

5.3 

369 

28.7 

Butt-rot. 

2.1 

1.2 

40.2 

70 

24.6 

62 

5.9 

Top-rot. 

Unknown rots. 

1.6 

1.0 

22.5 

46 

16.2 

72 

7.0 

.1 

.1 

18.9 

35 

12.3 

4 

1.0 

Combined. 

44.9 

26.1 

87.6 

284 


323 

30.9 


While only a few trees showed brown trunk-rot in comparison to 
those with red-brown butt-rot and yellow-brown top-rot, yet the 
volume of brown trunk-rot is greater than either of the others, 
particularly in board feet. This is due to the fact that brown trunk- 
rot when it does occur is quite likely to cause the loss of all or most 
of the merchantable portion of the affected tree. Yellow-brown top- 
rot and red-brown butt-rot, being localized, result in much less loss 
per tree, but make up for this in the many more trees with these 
decays. The greater loss through brown trunk-rot in board feet as 
compared to cubic feet in relation to red-brown butt-rot and yellow- 
brown top-rot is understood when it is remembered that the former 
is usually in the merchantable portion of the tree, while the latter 
two are often in the stump and top, which are not included in the 
board-foot volume but are figured in computing the cubic-foot volume. 

Furthermore, red-brown butt-rot is of more importance than the 
figures would indicate, since seriously affected trees are quite subject 
to windfall, breaking off near the ground. Then, too, this decay 
destroys the valuable heartwood of the butt logs. 

Of the total of 169 trees, 21 were free from decay, while in the 
remaining 148 there were 284 infections, or an average of 1.9 infections 
per infected tree. Some trees had as many as 6 individual infections. 
Again, in considering the infections conk-rot stands out both in the 
number of infections and particularly in the average volume of 
decay per infection. Trunk-rot has a high average volume of 
decay per infection, which shows again that this rot is of minor 
importance only because of the limited number of infections, but 
when a tree is once attacked destructive and extensive decay usually 
results 

MECHANICAL INJURIES. 

Mechanical injuries on trees are of importance in that besides some¬ 
times reducing the annual increment or causing an actual loss in 
merchantable volume from the mere presence of the injury they 
afford access to the heartwood of the tree for the spores of wood- 
destroying fungi. 

























6 


BULLETIN 1163, U. S. DEPARTMENT OP AGRICULTURE. 


Wounds in Douglas fir, though quite common, are mostly super¬ 
ficial and heal rather rapidly. Rapid healing is particularly the 
case in younger trees. Wounds as a rule callus very irregularly, and 
as a result it is usually difficult or impossible to determine the exact 
dates when scars were made and callused over by counting the annual 
rings. In this respect Douglas fir differs strikingly from the clear- 
cut, regular calluses characteristic of incense cedar and white fir. 
Furthermore, injuries in Douglas fir frequently result in the formation 
of prominent burls. 

Of the trees studied, only 11 were entirely free from scars. The 
remaining 158 trees had 508 scars, open and healed over, an average 
of 3.2 wounds per tree. Table 3 shows the relative frequency of the 
various types of scars 


Table 3. —Scars in Douglas fir. 


Type of scar. 

Number of scars, basis. 

Per¬ 
cent¬ 
age of 
total 
scars. 

Type of scar. 

Number of scars, basis. 

Per¬ 
cent¬ 
age of 
total 
scars. 

Open. 

Healed 

over. 

Total. 

Open. 

Healed 

over. 

Total. 

Fire scars. 

43 

237 

280 

55.1 

Spike tops 



10 

2.0 

Falling-tree scars... 

25 

61 

86 

16.9 

Broken tops . 



58 

11.4 

Lightning scars. 

11 

38 

49 

9.6 

Unknown scars.... 

0 


7 

1.4 

Sapsucker scars. 

1 

9 

10 

2.0 






Blaze scars. 

1 

0 

1 

.2 

Total. 



508 


Frost cracks. 

0 

7 

7 

1.4 






In Table 3 the healed-over, closed, or occluded scars are greatly in 
the majority. This indicates that the wounds were mostly superficial 
and that this tree species heals rapidly after wounding. 

The predominance of fire scars is striking. While it was not pos¬ 
sible to determine the years in which the fires occurred, for the reason 
stated previously, it was noticeable that most of the injuries of this 
nature had happened when the trees were relatively young—that is, 
below 20 inches diameter breast high, more or less. This coincides 
with our knowledge of fires in the Douglas fir region. In young 
stands fires which run over the surface of the ground injuring but 
not killing the trees are common, while in mature or overmature 
timber fires have a tendency to run through the crowns, killing all but 
scattered individuals outright. 

Burls may form as the result of fire scars, but more common are 
swollen, or churn, butts as the result of severe scars.. These churn 
butts extend usually from the ground level up the trunk slightly 
higher than the limit of the fire scar. Even though a fire scar has 
been healed over for a long time and there is no churn butt or burl 
to indicate its presence, it can often be detected by the variation 
in the appearance of the bark over the healed wound. This appear¬ 
ance is hard to describe, but not difficult to judge after a little 
experience. 

Next in numerical importance to fire scars were wounds caused by 
falling trees. These, of course, are more common in mature and 
overmature stands than in second growth. Trees may die and ulti¬ 
mately the snags will fall, or again large trees with butt-rot are 
quite subject to windfall. Such trees on their way down strike 
others, breaking off the tops or limbs or bruising the trunks and 
knocking off pieces of bark. Falling-tree scars rarely extend deeply 
into the tree. 

































DECAY IN DOUGLAS FIR. 


7 


Lightning wounds occasionally occurred, although the Douglas fir 
region is not subject to severe lightning storms. Injury by sap- 
suckers was rare,' and the few scars found were very superficial. 
These birds do not seem to select a single tree and attack it year 
after year, as they often do in other tree species. Frost cracks were 
not common. This was to be expected, since the Douglas fir region 
as a whole is not subject to sudden extreme variations of temper¬ 
ature from relatively warm to very cold. 

There were 10 spike-topped trees. Half of these dead tops had 
been caused by lightning, while two of them resulted from falling trees. 

On the other hand, trees with broken tops were not unusual. The 
most common cause of such injury was falling trees. This source 
accounted for 31 of the broken tops. Snow was responsible for 4 and 
lightning for 3, while the remaining 20 could not be determined. 
A load of ice or heavy wet snow is of more importance in causing 
broken tops than appears from these figures, but most of the damage 
occurs in young stands. According to observations of the writer and 
others, heavy snow or ice injury occurred about 1888 3 in the imme¬ 
diate section where this study was made. The damage was very 
apparent from the number of broken tops, all having been made at 
the same time, in second-growth timber. 

Broken tops require a long time to heal. Even after the volunteer 
top is well started the stub of the old top protrudes, and when this 
is finally grown over a slight crook still remains in the bole, which 
does not entirely disappear for years. 

In considering the data presented, it may appear from the total of 
508 scars on 158 trees that the trees were subject to excessive injury. 
It must be remembered that most of the wounds were superficial. 
Then, too, several small scars on a single tree might be made by the 
same agent. For example, one fire or one lightning stroke can 
readily cause several scars on a tree. Owing to the impossibility of 
determining with any accuracy the dates of injury in Douglas fir, it 
was necessary to consider each scar, with a few exceptions, as separate 
and distinct. 

ENTRANCE OF THE DECAYS. 

# 

The wind-blown spores from sporophores of wood-destroying fungi 
attacking the heartwood of living trees must light on exposed dead 
wood in order to cause infection. But the type of infection court 
varies with different species of decay, and it is of importance to 
determine the common means of entrance in each case, since in so 
far as the infections occur through controllable mechanical injuries 
there is a possibility of reducing the amount of loss. 

Table 4 shows the points of entrance for conk-rot. From this 
table it can be seen that knots or branch stubs are responsible for 
the major portion of the infections, and, what is far more important, 
all but an infinitesimal portion of the total volume of conk-rot 
resulted from these infections. 

The infections of brown trunk-rot both numerically and in the 
resulting volume of decay were rather more evenly distributed, as 
can be seen from Table 5; but here again knots predominate. 


* This date is from an unpublished record furnished by the Forest Service. 



8 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 

Table 4. —Infection court of conk-rot in Douglas fir. 



Infections. 



Percentage of total. 

Average volume. 

Infection court. 

Number, 

basis. 


Volume. 

) 


Number. 

Board 
• feet. 

Cubic 

feet. 

Board 

feet. 

Cubic 

feet. 

Knots . 

98 

83.0 

99.62 

99.48 

796 

77.0 

Fire scars.. . 

10 

8.5 

.04 

.03 

3 

.2 

Falling-tree wounds. 

3 

2.5 

0 

.05 

0 

1.4 

T,io''htning scars . . 

4 

3.4 

.34 

.43 

68 

8.2 

Dead tops.. 

Unknown scars . 

1 

2 

.9 

1.7 

0 

0 

0 

0 

0 

0 

0 

0 






t 



Table 5. —Infection court of trunk-rot in Douglas fir. 


Infections. 




Percentage of total. 


Infection court. 

Number, 

basis. 


Volume. 





Number. 

Board 

feet. 

Cubic 

feet. 

Board 

feet. 

Cubic 

feet. 

TCnots ... 

7 

46.7 

44.6 

46.1 

353 

28.4 

Fire scars. . 

2 

13.3 

0 

0 

0 

0 

Falling-tree scars . 

4 

26.7 

30.0 

26.9 

415 

29.0 

Tiight.ninp' scars . 

2 

13.3 

25.4 

26.9 

705 

58.0 









Table 6 brings out the relation between fire and red-brown butt-rot. 
The major portion of the infections entered through fire scars, and 
the resulting volume of decay was proportionately much higher. This 
imtt-rot also attacks the roots and can probably be spread by the con¬ 
tact of a diseased root with a sound one. About^ll per cent of the 
volume of rot is apparently traceable to this method of infection. 
Besides these two the other infection courts are of no importance. 


Table 6.— Infection court of butt-rot in Douglas fir. 


Infection court. 

Infections. 

Number, 

basis. 

Percentage of total. 

Average volume. 

Number. 

Volume. 

Board 

feet. 

Cubic 

feet. 

Board 

feet. 

Cubic 

feet. 

Knots. 

1 

1.4 

1.4 

0.5 

60 

2.0 

Fire scars. 

41 

58.6 

78.2 

79.1 

83 

8.0 

Falling-tree scars... 

4 

5.7 

3.7 

5 0 

40 

5.2 

Lightning scars. 

4 

o. 7 

2.5 

1.8 

28 

1.8 

Boots. 

16 

22.9 

10.8 

11.5 

29 

3.C 

Unknown scars. 

4 

5.7 

3.4 

2.1 

38 

2.2 















































































DECAY IN DOUGLAS EIR. 


9 


Yellow-brown top-rot, true to its name, in Table 7 shows the 
greatest number of infections entering through dead tops, which 
include broken and spike tops. Knots, though with fewer infections, 
were responsible for a greater volume of decay, since such infections 
usually occurred lower down on the bole where there was more 
heartwood for the fungus to work on than was the case when the 
wood destroyer entered through a dead top. The large volume of 
decay the cause of which is recorded as “ unknown” resulted from 
an extensive infection which could not be traced to its source. 


Table 7 .—Infection court of yellow-brown tojp-rot in Douglas fir. 


Infection court. 

Infections. 

Number, 

basis. 

Percentage of total. 

Average volume. 

Number. 

Volume. 

Board 

feet. 

Cubic 

feet. 

Board 

feet. 

Cubic 

feet. 

Knots. 

12 

26.1 

35.8 

35.7 

98 

9.6 

Fire scars.. 

2 

4.3 

8.2 

6.6 

135 

10.6 

Falling-tree scars. 

7 

15.2 

7.0 

1.9 

33 

.9 

Lightning scars. 

5 

10.9 

15.4 

15.0 

102 

9.7 

Dead tops. 

18 

39.1 

17.0 

23.8 

31 

4.3 

Unknown. 

2 

4.3 

16.7 

17.0 

275 

27.5 


Table 8 shows the infection courts of the unknown decays. Some 
of these were undoubtedly infections of the four common rots, but 
were abnormal or so small that they could not be accurately identified. 


Table 8. —Infection court of unknown rots in Douglas fir. 


Infection court. 

Infections. 

Number, 

basis. 

Percentage of total. 

Average volume. 

Number. 

Volume. 

Board 

feet. 

Cubic 

feet. 

Board 

feet. 

Cubic 

feet. 

Knots. 

5 

14.3 

0 

0 

0 

0 

Fire scars. 

12 

34.3 

80.0 

62.5 

10 

1.8 

Lightning scars. 

4 

11.4 

20.0 

8.8 

8 

.8 

Dead tops. 

11 

31.4 

0 

20.8 

0 

.6 

Roots. 

3 

8.6 

0 

7.8 

0 

.9 


In Table 9 the data in Tables 4 to 8, inclusive, have been combined. 
Knots were responsible for the greatest number of infections and a 
proportionately greater loss through decay. 

Of all the infection courts fire scars, which were only responsible 
for 4.2 per cent of the total rot volume, are the only factors that can 
be directly controlled. With the increase of efficiency in fire-protec¬ 
tion methods, injury from fires is being steadily reduced. But the 
other 95.8 per cent of the decay is traceable to sources that can not 
be controlled. Knots, falling trees, lightning, and snow or ice will 







































10 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 

be present in Douglas fir stands in the future, no matter how well 
regulated. Consequently, the reduction in the quantity of rot in 
Douglas fir by a reduction in the scars caused by controllable 
mechanical injuries can amount to little. 


Table 9. —Infection court of combined decays in Douglas fir. 



Infections. 



Percentage of total. 



Infection court. 

Number, 

basis. 


Volume. 

nvciago v uiuuiv. 



Number. 

Board 

feet. 

Cubic 

feet. 

Board 

feet. 

Cubic 

feet. 

Knots . 

123 

43.3 

89.2 

89.2 

664 

63.9- 

Fire scars. 

67 

23.6 

4.2 

4.2 

57 

5.5 

Falling-tree scars. 

18 

6.3 

2.2 

1.7 

114 

8.2 

Lightning scars... 

19 

6.7 

2.5 

2.4 

123 

11.5 

Dead tops . .. . 

30 

10.6 

.6 

1.0 

19 

2.8 

Roots. 

19 

6.7 

.5 

.6 

25 

2.6 

Unknown scars. 

8 

2.8 

.8 

.7 

88 

8.0 







While it is true that infection courts resulting from all mechanical 
injuries are of little importance in the total volume of decay produced 
as compared to knots or branch stubs, it is of academic interest to 
determine the kind of scar most susceptible to infection in the trees 
studied. This is brought out in Table 10. 


Table 10. —Susceptibility to infection of various scars in Douglas fir . 


Type of scar. 

Number 
of scars. 

Scars infected. 

Type of scar. 

Number 
of scars. 

Scars infected. 

Number. 

Per cent. 

Number. 

Per cent. 

Fire scars 

280 

67 

23.9 

Spike tops. 

* 

30 

44.1 

Falling-tree scars.. 

86 

18 

20.9 

Broken, tops. 

> 68 

Lightning scars ... 

49 

19 

38.8 

Unknown scars.... 

7 

7 

100 

Sapsucker scars ... 

10 

0 

0 





Blaze scars. 

1 

0 

0 

Total. 

5C8 

141 

28.0 

Frost cracks. 

7 

0 

0 






Dead tops, which include spike-tops and broken tops, followed 
by lightning scars, were most susceptible to infection, according to 
Table 10. 

INDICATIONS OF DECAY IN LIVING TREES. 

Recognition of the indications of decay in standing Douglas fir or 
in logs is of the greatest importance from a practical standpoint. 
A comparison of the cruise and actual cut on many operations in 
overmature decadent timber brings this out forcibly. At present 
there is a great deal of confusion and misinformation among foresters 
and lumbermen in regard to the detection of decay in living trees, 
and the specter of “hidden defect” assumes unnecessary proportions. 
In fact, decay in Douglas fir is more easily detected than in most 
species subject to a large amount of rot. 












































Bui. 1163, U. S. Dept, of Agriculture. 


Plate I 



Defective Douglas Firs Left Standing after Logging. 

The principal defect is decay caused by the ring-scale fungus. 


42198-23- 



































































Bui. 1163, U. S. Dept, of Agriculture. 


Plate II. 



A Practically Pure Stand of Overmature Douglas Fir after 

Logging. 

Nearly all the large pieces were left because of rot, principally decay caused by the 
ring-scale fungus. (Photographed by D. C. Ingram.) 






Bui. 1163, U . S. Dept, of Agriculture. 


Plate III 




Fig. I.—Conk-Rot Caused by Ring-Scale Fungus. Fig. 2.—Cross Section of a Douglas Fir Top. 

This illustrates the typical stage of the decay. In its incipient This shows the upper surface of a sporopho^e of the rose-colored fomes 

stages the rot is indicated by a reddish purple discoloration. and the yellow-brown rot caused by this fungus. 

















Bui. 1163, U. S. Dept, of Agriculture. 


Plate IV.H 



Sporophores of the Ring-Scale Fungus, Indicating Conk-Rot in the 

Heartwood of the Tree. 

(Photographed by G. G. Hedgcock.) 









Bui. 1163, U. S. Dept, of Agriculture. PLATE V. 



Fig. I.—Sporophores of the Velvet-Top Fungus on the Butt of a 

Living Douglas Fir. 

These sporophores indicate red-brown butt-rot in the tree. (Photographed by G. G. Hedgcock.) 



Only a thin shell of sapwood remains. Trees so badly decayed are subject to windfall, 
particularly if the rot extends into the roots. (Photographed by G. G. Hedgcock.) 







Bui. 1163, U. S. Dept, of Agriculture 


Plate VI. 



Fig. I.—Sporophore of the Quinine Fungus. 

These conspicuous whitish fruiting bodies are not common on living trees, but are found more 
often on dead down timber. The sporophore has a very bitter taste. 



Fig. 2.—Brown Trunk Rot Caused by the Quinine Fungus 

The decay is usually extensive in an infected tree. 






V 


Bui. 1163, U. S. Dept, of Agriculture. 


Plate VII. 



Burl on a Douglas Fir Left Standing on a Cut-Over Area. 

Because of the burl the tree was thought to be badly decayed. Burls dojiot indicate decay 

Compare with Plate VIII. 






Bu.. 1163, U. S. Dept, of Agriculture, 


Plate VIII 



Swollen Knots or Blind Conks on Douglas Fir 

These indicate conk-rot in the tree. Compare with Plate VII. 
















DECAY IN DOUGLAS FIR. 


11 


DEAD LIMBS. 

Large trees with many dead limbs in the lower crown are no more 
likely to be decayed than a normal tree. Such “wolf trees/’ as they 
are known to the forester, merely grew faster than their neighbors, 
and their branches did not die so soon through lack of light; conse¬ 
quently it requires a longer time for these large limbs to drop off 
and for the branch stub to heal over. 

BRANCH FANS. 

Groups of branches, radiating like a fan from one point, are not 
uncommon on Douglas fir. These branch fans have been considered 
by some persons as indications of decay. A little thought will show 
that this is not within the realm of probability. That decay in the 
dead heartwood could directly affect the vital growing portion of 
the trunk of a tree in such a way as to cause abnormal branching is 
directly contrary to all our knowledge of growth and development 
of trees. In all, these branch fans were found on 32 trees, varying 
from 1 to 15 on a single tree, with an average of 4.4. Of these 32 
trees, 2 were free from decay, while in 19 the infections were very 
light, rarely causing a loss of more than 10 board feet, and the branch 
fans were not on the same portion of the trunk as the decay. There 
was a considerable volume of decay in each of the 11 remaining 
trees, but in 7 of these the decay was in the lower or middle portion 
of the trunk, while the branch fans were above it in the crown. In 
only 4 trees were part or all of the branch fans found on the decayed 
section of the trunk. These figures indicate the complete lack of 
even an empirical relation between branch fans and decay. 

BURLS. 

Douglas fir when bruised is subject to burls at the point of injury, 
but it is questionable whether or not all burls are caused by wound¬ 
ing. Such burls are a disorganized mass of wood tissue with a 
gnarled or twisted grain. This formation is a direct response to the 
irritation caused by the injury. Burls are often considered to 
indicate decay. Plate VII shows a tree left uncut on a logging oper¬ 
ation because it was presumed from the presence of the burl that the 
tree was badly decayed. Data showing the relation of decay to burls 
in the trees studied are presented in Table 11. The number of burls 
to the tree varied from 1 to 20, with an average of 3.6. 


Table 11 .—Relation of burls to decay in Douglas fir. 


Character of data. 

Number. 

Per cent. 

Trees with hurls . ... 

43 


Trees with burls and no decay . ... 

6 

14.0 

Trees with burl 5 and decay on different sections of the trunk... 

19 

44.2 

Tree 5 with hu 1 *! 5 apd decav on the same section of the trunk ._. 

18 

41.9 



Analysis of the data in Table 11 demonstrates that the presence of 
burls does not mean decay in the tree. Of the trees with burls 14 
per cent were free from decay, while in 44.2 per cent the rot and 
burls did not occupy the same section of the bole. Burls on the 
butt of the tree, however, are sometimes an indication of decay, since 
burls in this position often result from wounding by fire, and fire 
scars are quite commonly infected with red-brown butt-rot. 












12 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 

CONK-ROT. 

The decay causing by far the greatest loss in Douglas fir is relatively 
easy to detect. Sporophores of this decay occur abundantly, this 
is indicated by the local name of conk-rot used in the Pacific JSorth- 
west. Lumbermen observed the unusually common occurrence ol 
sporophores, or u conks,” on infected trees, as compared to those 
with other decays, and the name followed. The prolific development 
of sporophores is shown by the fact that of 83 trees with sporophores 
there was an average of 14.4 per tree, or a total of 1,196. Considering 
all infections both with and without sporophores there was an average 
of 10.1 sporophores per infection, or 1 for every 6.34 cubic feet of 
conk-rot in the trees and 1 for every 65 board feet. 

It is of interest to consider the orientation of these sporophores. 
Moller (If), working with the same fungus, found 89.4 per cent of the 
sporophores on the westerly side of the trees. He explained this by 
the facts that the prevailing winds were from the west and the trees 
were most strongly struck by rain on the west side, and consequently 
the branch stubs (a very common point of infection) were more moist 
on that side. Weir and Hubert (7, p. 30), in their work with the Indian- 
paint fungus (Echinodontium tinctorium E. and E.) on western hem¬ 
lock (Tsuga JieteropJiylla (Raf.) Sarg.), found that most of the 
sporophores had a northwest to north-northeast orientation. The 
same workers ( 8 , p. 18), studying conk-rot in western white pine 
(.Pinus monticola Doug.), found the largest percentage of the sporo¬ 
phores develops on the west side of the tree, with the smallest per¬ 
centage on the southeast side. Table 12 shows the orientation of 
the sporophores on the trees studied. 

Table 12 . — Orientation of sporophores of conk-rot in Douglas fir. 


Orientation of sporophores. 


Character of data. 

NW. 

N. 

NE. 

E. 

SE. 

S. 

SW. 

W. 

Nnrrihfirnf sporophores. 

212 

291 

202 

91 

144 

77 

96 

79 

Percentage of total. 

17.8 

24.4 

17.0 

7.6 

12.1 

6.5 

8.1 

6.6 







The largest percentage of sporophores occurred on the north side 
of the trees and the smallest percentage on the south side. Adding 
the sporophores on the north, northwest, and northeast it is seen 
that 59.2 per cent were in the northerly grouping. Following this 
system gives 36.7 per cent easterly, 26.7 per cent southerly, and 32.5 
per cent westerly. The northerly direction clearly predominates. 
This is logically explained by the fact that there is less light on the 
northerly side and consequently more moisture, particularly during 
the growing season, which in this region is a long dry period inter¬ 
rupted by occasional thundershowers of brief duration. Conditions 
on the northerly side of the trees are therefore more favorable for 
infection and the subsequent development of sporophores. 

As a rule very little rot develops in a tree before a sporophore 
appears, or if not a sporophore at least a swollen knot, or “ blind 
conk,” as it is colloquially termed. The sporophores can not pene¬ 
trate the unbroken bark and issup only through knots or branch 


















DECAY IN DOUGLAS FIR. 


13 


stubs not yet occluded. A swollen knot is the initial stage of a 
sporophore in which the substance forming the conk is growing out 
through a knot and forcing out the bark. The pressure may also 
cause an increase in the width of the sap wood immediately around 
the knot, which accentuates the swelling. Swollen knots are illus¬ 
trated in Plate VIII. A swollen knot is just as good an indication 
of the presence of decay as a sporophore. Often the sporophore never 
develops beyond this stage, remaining abortive. Chopping into one 
of these knots reveals a brown, soft, corky or punky context, the same 
as in a fully developed sporophore. Plate III, Figure 1, shows a sec¬ 
tion through part of a decayed knot. 

The effect of fire on sporophores or swollen knots is striking. 
When mature timber is swept by fire, the flames running along the 
trunk of the tree can not burn off the thick bark. However, the 
corky context of the sporophores and decayed knots burns readily, 
and this results in rounded, blackened hollows extending for several 
inches into the tree where the fire has burned out the decayed knots. 
This makes it possible to judge in a measure the extent of conk-rot 
in recently fire-killed Douglas fir. 

That the development of swollen knots and sporophores follows 
rather closely the progress of conk-rot in the heartwood is brought 
out in Table 13. 

Table 13. —Relation of sporophores and swollen knots to conk-rot in Douglas fir. 


Decay. 


With sporophores. 

Without sporophores... 
With swollen knots-. 
Without swollen knots. 


Infections. 

Volume of decay. 



Percentage of total. 









.Average per 


Per¬ 





infection. 

Num¬ 

cent¬ 

Gross. 

Of conk-rot. 



ber, 

age of 







basis. 

total. 









Board 

Cubic 

Board 

Cubic 

Board 

Cubic 



feet. 

feet. 

feet. 

feet. 

feet. 

feet. 

96 

81.4 

36.83 

21.71 

95.94 

96.51 

782 

76.2 

22 

18.6 

1.56 

.78 

4.06 

3.49 

144 

12.0 

108 

91.5 

38.39 

22.49 

99.96 

99.97 

725 

70.2 

10 

8.5 

.01 

.01 

.04 

.03 

3 

.2 


Table 13 shows that while there was a noticeable percentage of the 
infections which did not develop sporophores, these infections were 
verv small, as is indicated by the volume percentages and the average 
volume per infection. The relation is even more striking with swollen 
knots, where the volume percentages and the average volume per in¬ 
fection of those infections without swollen knots is so small as to be 

n6 TMs b means, then, that it is possible to pick out rather accurately 
the trees in a stand affected with conk-rot. When high up m a tree 
among the branches swollen knots, or even sporophores, a re not easily 
seen but if overlooked there it does not make so much difference in 
the accuracy of an estimate, since the volume of the top logs is rel¬ 
atively insignificant in the total. 


EXTENT OF CONK-ROT. 


It is not only possible to pick out the decayed trees, but it is also 
feasible to judge with some exactness the normal extent of conk-rot. 

























14 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 

In the trees studied it was found that the average extent of decay, 
including typical and incipient decay, above the highest sporophore 
was 20.1 feet. This was based on 83 infections. In two infections 
the decay ended at the height of the top sporophore, and in one tree 
the rot extended for 61 feet above the highest sporophore. When 
the downward extent of conk-rot below the lowest sporophore was 
considered, it was necessary to discard those infections in which the 
decay extended into the stump. Based on only 33 infections, the 
average downward extent was 13.9 feet. The average of both 
upward and downward combined was 18.3 feet. 

The same figures for the highest and lowest swollen knots were as 
follows: Upward extent, 9.5feet, based on 93 infections; downward ex¬ 
tent, 9.2 feet based on 41 infections; combined average, 9.4 feet. In 
one tree the rot extended for 45.2 feet below the lowest swollen knot. 
This difference in the extent of decay beyond sporophores as 
compared to swollen knots is due to the fact that the swollen knot 
in many instances is the initial stage in the development of a normal 
sporophore, and consequently by the time a sporophore appears the 
decay has been in the tree longer and has progressed farther than at 
the formation of a swollen knot. 

These data mean, then, that it is possible to approximate the 
volume of conk-rot in defective trees when cruising. The figures, of 
course, should not be applied to an individual tree as such, but should 
be used in estimating the individual components of a stand in order 
to secure an accurate figure on the total loss through conk-rot. In 
actual practice the writer would use 20 feet as the upward or down¬ 
ward extent of decay beyond the highest or lowest sporophore and 
10 feet as the figure for swollen knots. In other words, in the case 
of a decayed tree with sporophores the trunk would be considered 
unmerchantable from a point 20 feet below the lowest sporophore to 
a point 20 feet above the highest sporophore, while for swollen knots 
the distance would be reduced to 10 feet below and above. These 
figures are easy to remember and have checked well with the writer’s 
observations since this study was made; but for greater accuracy in 
any given locality it is well to study felled trees and watch long logs 
through the mill, so that these limits can be corrected to fit"local 
conditions. 

RED-BROWN BUTT-ROT. 

Sporophores are, of course, the best indication of decay. The 
sporophores of red-brown butt-rot being annual are not common 
except in favorable seasons for their development, but can always 
be found now and then in a locality where the trees are affected. 
However, the best clue is fire scars. Noticeably fire-scarred trees 
are commonly infected with this decay. Of the 125 trees with fire 
scars that were studied, 41, or 33 per cent, were infected with red- 
brown butt-rot. Healed fire scars can often be detected by a 
variation in the appearance of the bark over the wound or by 
swollen or churn butts. There are no swollen knots with this decay. 

BROWN TRUNK-ROT. 

Brown trunk-rot is rather hard to detect. Swollen knots are not 
formed. Sporophores are rare on living trees, but when they do 
occur they are very conspicuous and not readily overlooked. 


DECAY IN DOUGLAS FIE. 


15 


Furthermore, observation shows that they indicate extensive decay in 
the tree. Only one tree studied had sporophores of this rot, and the 
decay volume in cubic feet was 31 per cent and in board feet 74 per 
cent of the gross volume of the tree. But the total loss caused by 
this decay was trifling. (See Table 2.) 

YELLOW-BROWN TOP-ROT. 

Yellow-brown top-rot also is rather hard to judge. Swollen knots 
do not accompany the decay. Sporophores are not uncommon, 
particularly with the more extensive infections. In the trees studied, 
seven infections, which resulted in 42 per cent of the cubic-foot 
volume and 41 per cent of the board-foot volume of yellow-brown 
top-rot, had developed sporophores. However, the sporophores are 
commonly so high up in the trees that they are easily overlooked 
and, in fact, are often completely hidden by the branches. Broken 
or spike tops commonly indicate infection (see Table 7). The 
aggregate loss caused by this decay is small. 

INDICATIONS OF DECAY IN FELLED TIMBER. 

The estimate of the extent of defect in logs or felled timber is 
much easier than in standing trees. The red-brown butt-rot is 
revealed in the butt cut, and its upward extent can be more closely 
approximated. Knots can be tested carefully for signs of rot, and if 
the timber has been bucked the ends of the logs can be examined for 
typical decay or the discolorations caused by incipient decay. How¬ 
ever, if the logs have been exposed to the weather for several months 
these discolorations fade and can not be seen. 

It is notf at all difficult to judge quite accurately the extent of 
conk-rot in felled Douglas fir by chopping into the knots to reveal 
the brown corky context of the abortive sporophore. 

EXTENT OF INCIPIENT DECAY. 

A knowledge of the vertical extent of incipient decay, which is the 
term used to designate the early stages of rot, beyond the typical 
decay or well-advanced rot is of practical value. In some infections 
the incipient decay may end with the typical decay and in other 
cases extend many feet beyond it. The horizontal or radial extent 
normally amounts to only a few inches. Incipient decay, which is 
usually indicated by a discoloration of infected wood, in some cases 
pronounced and in others so faint as to be practically invisible, is 
not always easy to detect. Affected wood in a casual examination 
seems to be firm and strong. Consequently, it is the rule rather 
than the exception in the lumber trade to include incipient decay 
with sound lumber. 

Wood is weakened by incipient decay, the degree depending on 
the stage of the rot and also on the species of fungus at work. Tests 
(3) on Douglas fir with incipient decay of conk-rot showed that the 
wood was apparently not weakened, but pieces with incipient decay 
of red-brown butt-rot and brown trunk-rot, to which general type of 
decay yellow-brown top-rot also belongs, were much reduced in 
strength. Furthermore, if infected material is merely air dried, the 
hyphse may remain dormant, ready to continue to decay the wood 
again if suitable conditions arise. Hence, wood with incipient decay 


16 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 

should be excluded from all lumber to be used for purposes requiring 
strength and durability. 

The incipient stage of conk-rot is often quite extensive. In one 
tree this stage of decay extended for 29.6 feet vertically in the heart- 
wood beyond the typical decay, while in several infections this figure 
ranged from 10 to 20 feet. The average extent upward of incipient 
decay beyond the typical decay was 3.3 feet and the average extent 
downward was 4 feet. The significance of this difference will be 
touched upon later. The average extent both up and down was 3.5 
feet, based on 145 measurements. 

Red-brown butt-rot is less variable in respect to the extent of 
incipient decay. The greatest extent found was 8.4 feet, while the 
average based on 44 measurements was 1.95 feet. This average is 
based on measurements of upward extent only, since most of the 
infections began in the stump or extended into it and no downward 
measurements were possible. 

Only meager data were available on brown trunk-rot. Based on 
13 measurements the upward extent of the incipient decay was found 
to be 3.5 feet, while the downward extent was 3.6 feet. The com¬ 
bined average was 3.6 feet. The extreme extent was 8.5 feet above 
typical decay. 

The incipient decay of yellow-brown top-rot had an average extent 
upward of 2.2 feet and downward of 3.8 feet, while the combined 
average was 3.1 feet, based on 58 measurements. In one tree incip¬ 
ient decay extended up beyond typical decay for a distance of 25.4 
feet. 

From the foregoing it can be seen that in all three of the rots in 
which it was possible to make a comparison between the upward 
and downward extent of incipient decay the downward extent 
exceeded the upward on the average, and the difference is most strik¬ 
ing in yellow-brown top-rot, where most of the infections occur in 
the upper part of the bole. This difference is probably explained by 
the well-known fact that older trees are much more subject to decay 
than younger ones, and therefore it follows that older heartwood is 
more susceptible than younger. As the fungus progresses downward 
in the heartwood of a tree it encounters wood gradually increasing 
in age and easier to decay, while as it moves upward younger wood 
which offers more resistance is continually invaded, decreasing the 
extent of both typical and incipient decay. This tendency for clecay 
to work more rapidly downward than upward is in keeping with 
other observations (I, p. 21). 

The figures presented on the extent of incipient decay show that 
this is quite variable and indicate the need for careful inspection to 
eliminate this type of defect from timbers where durability and 
strength are a prerequisite. 

SUMMARY. 

The four principal decays in Douglas fir are conk-rot caused by 
the ring-scale fungus (Trametes pini ), red-brown butt-rot caused by 
the velvet-top fungus (Polyporus schweinitzii ), brown trunk-rot 
caused by the quinine fungus (Fomes lands), and yellow-brown top- 
rot caused by the rose-colored Fomes (Fomes roseus). Conk-rot and 
brown trunk-rot usually occur in the body of the trunk, red-brown 
butt-rot is commonly confined to the stump and first log, while yellow- 


DECAY IN DOUGLAS FIR. 


17 


brown top-rot usually occurs in the upper bole or top. Conk-rot 
causes by far the greatest volume of decay. The other three rots 
are of relatively minor importance, except that red-brown butt-rot 
predisposes an infected tree to windfall. 

Douglas fir is subject to wounding throughout its life and partic¬ 
ularly to injury by fire during its earlier years. On the whole, wounds 
in Douglas fir are mostly superficial, and this tree species heals 
rapidly after wounding. Scars callus very irregularly, and it is 
usually difficult or impossible to determine the exact dates when 
scars were made. 

Mechanical injuries are of little importance in relation to the 
entrance of decay. Knots were responsible for nearly 90 per cent of 
the volume of all decay in the trees studied. Fire scars were the 
entrance point for 4 per cent, and the remaining 6 per cent came in 
through other scars. Fire is the only factor which is controllable, so 
there can be but little reduction in the extent of decay in future 
stands by a reduction in the scars caused by controllable mechanical 
injuries. 

Recognition of the indications of decay in standing or felled timber 
is of the greatest importance from a practical standpoint, yet this is 
little understood. Branch fans, dead limbs, or burls do not indicate 
decay. Sporophores and swollen knots which develop prolifically 
indicate the presence of conk-rot. After a stand has been fire swept, 
burned-out hollows show where there were sporophores and swollen 
knots. It is also possible to approximate with some accuracy the 
volume of the decay. Conk-rot, on the average, extended approxi¬ 
mately 20 feet in the trunk beyond the highest or lowest sporophore 
and 10 feet beyond the highest or lowest swollen knot. Sporophores 
of red-brown butt-rot are not common. However, the relative fre¬ 
quency of fire scars indicates somewhat the relative amount of this 
decay. Churn butts often denote old fire scars. Brown trunk-rot 
is rather difficult to detect in standing trees, but the loss caused by 
this decay is insignificant. This also applies to yellow-brown top-rot. 

Figures on the different rots, giving the extent of incipient decay 
beyond typical decay, show that this is rather variable, thus requir¬ 
ing careful inspection to obviate the inclusion of wood with this type 
of defect in timbers selected for durability and strength. 

OUTLOOK. 

The work on which the preceding discussion is based is merely pre¬ 
liminary. More extensive studies are needed to bring out new facts 
and develop still further those already brought out. This should 
aid materially in placing the estimating of Douglas-fir timber on a 
more exact basis. • 

The biggest problems remain unsolved. Our half-formulated ideas 
of control of decay in Douglas fir are based on observation without 
a sound backing of exact data. Furthermore, while it is a well- 
established fact that young stands or second growth are relatively 
immune from decay, it is not yet determined at what age in the life 
of the stand this immunity ceases and the trees become subject to 
extensive decay. Establishing this age will enable us in the future 


18 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 


to cut stands before there is any real loss and at the same time per¬ 
mit the trees to attain the maximum size. 

Equally important is the periodic rate of increase in the loss through 
decay after the above age has been passed. Such information is of 
the highest value to organizations holding extensive stands of mature 
or overmature timber, enabling them to estimate the loss in their 
holdings and adapt plans accordingly. But these questions can only 
be answered by the study of all the trees felled and left standing on 
a wide range of plats in stands of different ages and conditions 
selected on logging operations throughout the Douglas-fir region of 
the Pacific Northwest. 


LITERATURE CITED. 


(1) Boyce, T. S. 

1920. The dry-rot of incense cedar. U. S. Dept. Agr. Bui. 871, 58 p., 3 fig., 

3 pis., 11 tables. Literature cited, p. 57-58. 

(2) Chapman, Herman Haupt. 

1921. Forest mensuration, xxii, 553 p., 88 fig., 89 tables. New York. 

(3) Colley, R. H. 

1921. The effect of incipient decay on the mechanical properties of airplane 
timber. (Abstract.) In Phytopathology, v. 11, p. 45. 

(4) Moller, A. 

1904. Uber die Notwendigkeit und Moglichkeit wirksamer Bekampfung des 
Kiefernbaumschwammes Trametes Pini (Thore) Fries. In Ztschr. 
Forst. u. Jagdw., Jahrg. 36., p. 677-715, pi. 4-5. 

(5) U. S. Dept. Agr., Forest Service. 

1916. Instructions for the scaling and measurement of national forest timber. 
94 p., 10 tables. Washington, D. C. 

(6) 1920. Timber depletion, lumber prices, lumber exports, and concentration of 

timber ownership. 71 p., 22 fig., 26 tables. Washington, D. C. 

(7) Weir, James R., and Hubert, Ernest E. 

1918. A study of heart-rot in western hemlock. TJ. S. Dept. Agr. Bui. 722, 
39 p., 13 fig. Bibliographical footnotes. 

(8) 1919. A study of the rots of western white pine. U. S. Dept. Agr. Bui. 799, 

24 p. Bibliographical footnotes. 


19 




L I . BRARY 0F congress 


0 002 811 592 1 


ORGANIZATION OF THE 

UNITED STATES DEPARTMENT OF AGRICULTURE. 


Secretary of Agriculture . 

Assistant Secretary . 

Director of Scientific Work . 

Director of Regulatory Work . 

Weather Bureau . 

Bureau of Agricultural Economics . 

Bureau of Animal Industry . 

Bureau of Plant Industry ... 

Forest Service . 

Bureau of Chemistry . 

Bureau of Soils . 

Bureau of Entomology . 

Bureau of Biological Survey . 

Bureau of Public Roads . 

Fixed Nitrogen Research Laboratory . 

Division of Accounts and Disbursements . 

Division of Publications . 

Library . 

States Relations Service . 

Federal Horticultural Board . 

Insecticide and Fungicide- Board . 

Packers and Stockyards Administration 
Grain Future Trading Act Administration... 
Office of the Solicitor 


Henry C. Wallace. 

C. W. Pugsley. 

E. D. Ball. 

Charles F. Marvin, Chief. 

Henry C. Taylor, Chief. 

John R. Mohler, Chief. 

William A. Taylor, Chief. 

W. B. Greeley, Chief. 

Walter G. Campbell, Acting Chief.. 
Milton Whitney, Chief. 

L. 0. Howard, Chief. 

E. W. Nelson, Chief. 

Thomas H. MacDonald, Chief. 

F. G. Cottrell, Director. 

A. Zappone, Chief. 

Edwin C. Powell, Acting Chief. 
Claribel R. Barnett, Librarian. 

A. C. True, Director. 

C. L. Marlatt, Chairman. 

J. K. Haywood, Chairman. 

Chester Morrill, Assistant to the. 
Secretary. 

R. W. Williams, Solicitor. 


:} 


This bulletin is a contribution from 


Bureau of Plant Industry... 
Office of Investigations in 

20 


. William A. Taylor, Chief. 

Forest Pathology. Haven Metcalf, Pathologist in 
Charge. 


ADDITIONAL COPIES 

OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 

AT 

10 CENTS PER COPY 

PURCHASER AGREES NOT TO RESELL OR DISTRIBUTE THIS 
COPY FOR PROFIT.—PUB. RES. 57, APPROVED MAY 11, 1922 

V 



























